The present invention relates to elastomer surfaces and a process for providing an elastomer surface, and in preferred embodiments, a fluoroelastomer, hydrofluoroelastomer or VITON.RTM. hydrofluoroelastomer surface, on a supporting substrate. The resulting surfaces are useful as surfaces for components in electrostatographic processes, especially xerographic processes, including digital, image on image and contact electrostatic printing applications. The elastomer surfaces are useful as coatings for fuser members including donor members, pressure members, fuser or fixing members, toner transfer members, and like members. In embodiments, the present invention allows for a decrease in the number of steps normally necessary for preparing a coated fuser member, which decreases the unit manufacturing cost and decreases the time necessary for preparation of the fuser member. In general, with the present process, instead of coating an adhesive on a fuser member followed by coating a fluoroelastomer topcoat thereon, an adhesive or primer is mixed with the fluoroelastomer material and the adhesive/fluoroelastomer mixture is coated on the fuser member. The resulting elastomer coating has increased adhesion to the fuser member, resulting in a decrease in delamination of the elastomer layer, which in turn, results in longer fuser life.
In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles which are commonly referred to as toner. The visible toner image is then in a loose powdered form and can be easily disturbed or destroyed. The toner image is usually fixed or fused upon a support which may be the photosensitive member itself or other support sheet such as plain paper.
To fuse electroscopic toner material onto a support surface permanently by heat, it is usually necessary to elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce and become tacky. This heating causes the toner to flow to some extent into the fibers or pores of the support member. Thereafter, as the toner material cools, solidification of the toner material causes the toner material to be firmly bonded to the support.
Typically, the thermoplastic resin particles are fused to the substrate by heating to a temperature of between about 90.degree. C. to about 200.degree. C. or higher depending upon the softening range of the particular resin used in the toner.
Several approaches to thermal fusing of electroscopic toner images have been described. These methods include providing the application of heat and pressure substantially concurrently by various means, a roll pair maintained in pressure contact, a belt member in pressure contact with a roll, and the like. Heat may be applied by heating one or both of the rolls, plate members or belt members. The fusing of the toner particles takes place when the proper combination of heat, pressure and contact time is provided. The balancing of these parameters to bring about the fusing of the toner particles is well known in the art, and can be adjusted to suit particular machines or process conditions.
It is important in the fusing process that no offset of the toner particles from the support to the fuser member takes place during normal operations. Toner particles offset onto the fuser member may subsequently transfer to other parts of the machine or onto the support in subsequent copying cycles, thus increasing the ba background or interfering with the material being copied there. The referred to "hot offset" occurs when the temperature of the toner is increased to a point where the toner particles liquefy and a splitting of the molten toner takes place during the fusing operation with a portion remaining on the fuser member. The hot offset temperature or degradation of the hot offset temperature is a measure of the release property of the fuser roll, and accordingly it is desired to provide a fusing surface which has a low surface energy to provide the necessary release. To ensure and maintain good release properties of the fuser roll, it has become customary to apply release agents to the fuser roll during the fusing operation. Typically, these materials are applied as thin films of, for example, silicone oils to prevent toner offset.
Particularly preferred fusing systems are comprised of a heated cylindrical fuser roll having a fusing surface which is backed by a cylindrical pressure roll forming a fusing nip therebetween. A release agent donor roll is also provided to deliver release agent to the fuser roll. While the physical and performance characteristics of each of these rolls, and particularly of their functional surfaces are not precisely the same depending on the various characteristics of the fusing system desired, the same classes of materials are typically used for one or more of the rolls in a fusing system in an electrostatographic printing system.
Fusing systems using fluoroelastomers as fuser members are described in U.S. Pat. No. 4,264,181 to Lentz et al., U.S. Pat. No. 4,257,699 to Lentz, and U.S. Pat. No. 4,272,179 to Seanor, all commonly assigned to the assignee of the present invention.
U.S. Pat. No. 5,017,432 describes a fusing surface layer obtained from a specific fluoroelastomer, poly (vinylidenefluoride hexafluoropropylene tetrafluoroethylene) where the vinylidenefluoride is present in an amount less than 40 weight percent. The patent further discloses curing the fluoroelastomer with VITON.RTM. Curative No. 50 (VC-50) available from E.l. Du Pont de Nemours, Inc. which is soluble in a solvent solution of the polymer at low base levels and is readily available at the reactive sites for crosslinking. The patent also discloses use of a metal oxide (such as cupric oxide) in addition to VC-50 for curing.
U.S. Pat. No. 5,061,965 to Ferguson et al., discloses an elastomer release agent donor layer comprising poly(vinylidenefluoride-hexafluoropropylene-tetrafluoroethylene) and a metal oxide, where the vinylidenefluoride is present in an amount less than 40 weight percent. The release agent donor layer is cured with a nucleophilic curing agent in the presence of an inorganic base.
U.S. Pat. Nos. 5,338,587 and 5,366,772 disclose mixing a fluoroelastomer with a nucleophilic curative and methyl ethyl ketone solvent and spray coating the solution onto the roll.
U.S. Pat. No. 5,700,568 discloses a fusing surface which is prepared in the absence of metal oxides and wherein the outer fluoroelastomer layer is the reaction product of a fluoroelastomer, a polymerization initiator, a polyorganosiloxane and an amino silane.
U.S. Pat. No. 5,744,200 discloses a volume grafted elastomer prepared by dissolving a fluoroelastomer in a solvent, adding a nucleophilic dehydrofluorinating agent, preferably an amino silane which acts as both a dehydrofluorinating agent and curing agent, a polymerization initiator and a polyorganosiloxane in amounts sufficient to effect formation of a volume grafted fluoroelastomer, and providing a layer of the volume grafted fluoroelastomer to a substrate.
U.S. Pat. No. 5,695,878 discloses fluoroelastomer surfaces prepared by dissolving a fluoroelastomer, adding an amino silane to form a homogeneous fluoroelastomer solution, and providing a layer of the homogeneous fluoroelastomer solution to the supporting substrate.
U.S. Pat. No. 5,750,204 discloses fluoroelastomer surfaces prepared by dissolving a fluoroelastomer in a solvent, adding an amino silane to effect coupling and crosslinking and to form a resulting homogeneous fluoroelastomer solution, and subsequently providing a layer of the homogeneous fluoroelastomer solution to the supporting substrate.
U.S. Pat. No. 5,753,307 discloses fluoroelastomer surfaces prepared by dissolving a fluoroelastomer in a solvent, adding a dehydrofluorinating agent, adding an amino silane to form a resulting homogeneous fluoroelastomer solution, and subsequently providing at least one layer of the homogeneous fluoroelastomer solution to a substrate.
U.S. patent application Ser. No. 08/822,521 filed Mar. 26, 1997, discloses a flow coating solution comprising a fluoroelastomer, a nucleophilic crosslinking agent, and an effective solvent.
U.S. patent application Ser. No. 08/824,576 filed Mar. 26, 1997, discloses a fuser member comprising: a) a substrate; and thereover b) an amino silane adhesive coating comprising an amino silane composition and an organic phosphonium catalyst; and having thereon, c) a fluoroelastomer outer coating comprising a fluoroelastomer.
Generally, the process for providing the elastomer surface on the supporting substrate, e.g., donor member, pressure member, fuser member, toner transfer member, or like substrates, includes preparing a layered structure including, in order, 1) a fuser member substrate which can be a stainless steel or aluminum cylindrical core, 2) an adhesive layer, 3) a high temperature vulcanization (HTV) silicone rubber base layer which may include a thermally conductive filler, peroxide curative and colorant, 4) an adhesive or primer layer, and 5) at least one layer of preferably fluoroelastomer which may contain carbon black, and may include crosslinking agents and curing agents.
Therefore, a more cost effective and less time consuming method of providing a fluoroelastomer surface, which results in elastomers having sufficient bonding strength to lessen the occurrence of delamination is desired.